93 



age 9660 per gram (see Table 2). The average content per gram 

 of these three pancreases was 9623 islands, the average content per 

 gram of the five adults in Table 1 was 13350. The high average 

 and maxinmm of the head in this series was due to the unusually high 

 count in this portion of the pancreas of one case, and does not jus- 

 tify the conclusion that this portion of the pancreas usually contains 

 more islands than the other two portions, since in two out of the three 

 cases the counts were in accord with Opie's finding of a larger content 

 in the tail of the organ. 



It is apparent from the foregoing that the estimates of the number 

 of islands in the pancreas made by previous observers is far below 

 the real number, and that the percentage of error by this method 

 of computation is much greater with some observers than with others. 

 There seems to be little room for doubt that the principal source 

 for this error is to be found in the overlooking of large numbers of 

 the smaller islands in counting, owing to the lack of sufficiently dis- 

 criminative staining methods. Furthermore, since the same error 

 enters into the computation of the total volume of island tissue, such 

 estimates must be far below the real content, even in the case of the 

 estimates made by Heiberg, who paid special attention to the smaller 

 islands, and accordingly approached more closely, in his estimate to 

 the real number. 



I had entertained hopes that this method of studying the is- 

 lands of Langerhans might be employed on autopsy subjects, but at- 

 tempts at transfusion on four subjects recently dead have in every 

 case given such discouraging results that it is doubtful whether the 

 method is generally applicable to any extent except subjects dead 

 by violence. 



In conclusion I wish to express my thanks to Drs. Molloy and 

 Smith of the Bureau of Health for the Philippine Islands for their 

 courtesy in placing this material at my disposal, and to Dr. R. M. 

 Lhamon of this laboratory for assistance in counting islets. 



Bibliography. 



Bensley, E. R., 1911, Studies on the pancreas of the guinea pig. Amer. Jour, 

 of Anat., Vol. 12, 297. 



Dewitt, L. M., 1906, Morphology and Physiology of the areas of Langerhans 

 in some vertebrates. Jour. Exper. Med., Vol. 8, 193. 



Heiberg, K. A., 1906, Beiträge zur Kenntnis der LANGERHANSschen Inseln 

 im Pankreas, nebst Darstellung einer neuen mikroskopischen Messungs- 

 methode. Anat. Anz., Vol. 29, 49. 



